Pressurized dispensing systems, commonly referred to as aerosols, experienced first significant commercialization in the early 1950s resulting in a proliferation of products.
Despite their high costs, aerosol products gained immediate consumer acceptance. The single most important factor behind this success story is the convenience offered by these pressurized products.
Recently, the aerosol market was thrown into a state of disarray as a result of the Rowland-Mollina ozone depletion theory which hypothesizes that a certain percentage of halohydrocarbon propellants find their way to the stratosphere causing a depletion of ozone in that stratum. With a depletion of the ozone in the stratosphere, a greater amount of ultraviolet radiation enters the atmosphere resulting in an increased incidence of skin cancer.
Packaging alternatives of halohydrocarbon propelled aerosols include: products propelled with liquefied hydrocarbon propellants (LPG) such as butane, isobutane and propane and mixtures thereof. Because of the flammability of the LPG gases a substantial amount of water is necessary in the formulation to provide a dousing effect. Products propelled with compressed gas propellants such as nitrogen or the more soluble nitrous oxide and carbon dioxide are usually quite wet because their low solubilities and low concentrations (as compared with halohydrocarbon and hydrocarbon propellants) deprive the product of breakup power. Combinations of liquefied and compressed gas propellants offer no synergistic advantage in terms of achieving a dry spray.
There are, also, the ever-present dangers of aerosols: flammability (in the case of hydrocarbon propelled products), explosion hazard, inhalation toxicity potential, inadvertent misuse of product, valve malfunction, etc.
Pump sprays are high cost, low efficiency substitutes for pressurized products. Antiperspirant pump sprays are currently on the market as non-aerosol counterparts. Their acceptance, has been poor primarily because of the wetness of the application.
Other packaging forms including separative devices, elastomeric membranes with a memory, spring loaded devices, etc., are of little commercial value because of the inordinately high cost, the exotic nature of the hardware and the lack of basic improvement over existing lower cost systems.
In addition to spray application, another means of applying antiperspirant products is by powder application. The major disadvantages of conventional powder products include dusting and lack of adhesion.
In 1979, sales of roll-on antiperspirant and deodorant increased significantly due to the disenchantment of the public with aerosol products and the introduction of new products in roll-on form such as the suspension of antipersipirant salts in a volatile silicone (Gillette's "Dry Idea") and powder roll-ons (such as Carter Product's "Arrid Dry Powder Roll-on"). Roll-on deodorants/antiperspirants are, additionally, more effective than other product forms such as aerosol and pump sprays in reducing sweat.
Roll-on deodorants and antiperspirants, however, suffer from the lack of application aesthetics. The average aqueous roll-on lotion takes a long time to dry and passes through an uncomfortable sticky and tacky stage prior to drying. Attempts to overcome these negative attributes have not been entirely successful. The solution to one problem gave rise to other problems. For example, although the suspension of antiperspirant salts applied by roll-on means eliminated the sticky/tacky sensation, the oiliness from the volatile silicone vehicle persists for fifteen minutes, more or less.
Although dry powder roll-ons eliminate the sticky/tacky sensation and are not oily, the adhesion of the application is very poor; the powdery material falls out on the clothing and in the general vicinity of the application. The powder does not flow readily between the ball and housing and the net result may be less than the desirable amount of product applied to the axilla with commensurately less efficacy.
Recently, it was discovered that aerated, hydrophobic metal powder oxide microencapsulated aqueous droplets could be formulated in a powder-like dry feeling shear-sensitive suspension. However, when this suspension is subjected to shear such as by passage through the outlet orifice of a spray container or by rubbing, combing, etc., the droplets coalesce to form a smooth, elegant cream or lotion having good adhesion to a surface.
Bioaffecting materials such as antiperspirants or deodorants can be added to the powder or aqueous phase of the bulk liquid-in-air emulsion or suspension without affecting its ability to form a stable, shear-sensitive suspension or its ability to dispense the particles thereof. The microencapsulated suspension is the subject of U.S. patent applications Ser. Nos. 29,630 and 160,673 now issued as U.S. Pat. Nos. 4,278,206 and 4,364,515, respectively.
Roll-on applicators operate by attaching material to the underside of the ball and conveying the suspension to the axilla where it is deposited. It was not known nor believed that the powdery-like suspension would adhere to the ball since it does not adhere to most surfaces nor was it known whether the powder suspension nor the sheared lotion or cream form thereof would permit consistent operation of the roll-on applicator without fouling or seizing of the ball.